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  • richardmitnick 1:12 pm on September 25, 2014 Permalink | Reply
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    From Daily Galaxy: “Hubble Captures a Newly Formed Galaxy in Our Cosmic Neighborhood” 

    Daily Galaxy
    The Daily Galaxy

    September 25, 2014
    No Writer Credit

    ddo

    Elderly galaxies tend to be larger thanks to collisions and mergers with other galaxies that have bulked them out, and are populated with a variety of different types of stars — including old, young, large, and small ones. Their chemical makeup is different too. Newly-formed galaxies have a similar composition to the primordial matter created in the Big Bang (hydrogen, helium and a little lithium), while older galaxies are enriched with heavier elements forged in stellar furnaces over multiple generations of stars.
    Dwarf galaxy DDO 68, captured by the NASA/ESA Hubble Space Telescope, was one of the best candidates so far discovered for a newly-formed galaxy in our cosmic neighborhood. The galaxy lies around 39 million light-years away from us; although this distance may seem huge, it is in fact roughly 50 times closer than the usual distances to such galaxies, which are on the order of several billions of light years.

    NASA Hubble Telescope
    NASA/ESA Hubble

    Astronomers usually have to peer very far into the distance to see back in time, and view the Universe as it was when it was young. This new NASA/ESA Hubble Space Telescope image of galaxy DDO 68, otherwise known as UGC 5340, was thought to offer an exception. This ragged collection of stars and gas clouds looks at first glance like a recently-formed galaxy in our own cosmic neighbourhood. But, is it really as young as it looks?

    Astronomers have studied galactic evolution for decades, gradually improving our knowledge of how galaxies have changed over cosmic history. The NASA/ESA Hubble Space Telescope has played a big part in this, allowing astronomers to see further into the distance, and hence further back in time, than any telescope before it — capturing light that has taken billions of years to reach us.

    Looking further into the very distant past to observe younger and younger galaxies is very valuable, but it is not without its problems for astronomers. All newly-born galaxies lie very far away from us and appear very small and faint in the images. On the contrary, all the galaxies near to us appear to be old ones.

    By studying galaxies of various ages, astronomers have found that those early in their lives are fundamentally different from those that are older. DDO 68 looks to be relatively youthful based on its structure, appearance, and composition. However, without more detailed modelling astronomers cannot be sure and they think it may be older than it lets on.

    DDO 68 is the best representation yet of a primordial galaxy in the local Universe as it appears at first glance to be very low in heavier elements — whose presence would be a sign of the existence of previous generations of stars.

    lg
    Local Group

    Hubble observations were carried out in order to study the properties of the galaxy’s light, and to confirm whether or not there are any older stars in DDO 68. If there are, which there seem to be, this would disprove the hypothesis that it is entirely made up of young stars. If not, it would confirm the unique nature of this galaxy. More complex modelling is needed before we can know for sure but Hubble’s picture certainly gives us a beautiful view of this unusual object.

    The image is made up of exposures in visible and infrared light taken with Hubble’s Advanced Camera for Surveys.

    NASA Hubble ACS
    Hubble ACS

    See the full article here.

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  • richardmitnick 1:43 pm on September 24, 2014 Permalink | Reply
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    From Hubble: “Clear skies on exo-Neptune” 

    NASA Hubble Telescope

    Hubble

    24 September 2014

    Contacts

    Nikku Madhusudhan
    University of Cambridge
    United Kingdom
    Tel: +1 617 475 5112
    Cell: +44 7804 419140
    Email: nmadhu@ast.cam.ac.uk

    Jonathan Fraine
    University of Maryland
    USA
    Tel: +1-301-405-1469
    Email: jfraine@astro.umd.edu

    Drake Deming
    University of Maryland
    USA
    Tel: +1-301-405-8053
    Email: ddeming@astro.umd.edu

    Georgia Bladon
    ESA/Hubble, Public Information Officer
    Garching bei München, Germany
    Cell: +44 7816291261
    Email: gbladon@partner.eso.org

    Astronomers using data from the NASA/ESA Hubble Space Telescope, the Spitzer Space Telescope, and the Kepler Space Telescope have discovered clear skies and steamy water vapour on a planet outside our Solar System. The planet, known as HAT-P-11b, is about the size of Neptune, making it the smallest exoplanet ever on which water vapour has been detected. The results will appear in the online version of the journal Nature on 24 September 2014.

    NASA Spitzer Telescope
    NASA/Spitzer

    NASA Kepler Telescope
    NASA/Kepler

    hat
    Size comparison of HAT-P-11b (gray) with Neptune.

    hatb
    Image credit: NASA/JPL-Caltech

    The discovery is a milestone on the road to eventually finding molecules in the atmospheres of smaller, rocky planets more akin to Earth. Clouds in the atmospheres of planets can block the view of what lies beneath them. The molecular makeup of these lower regions can reveal important information about the composition and history of a planet. Finding clear skies on a Neptune-size planet is a good sign that some smaller planets might also have similarly good visibility.

    “When astronomers go observing at night with telescopes, they say ‘clear skies’ to mean good luck,” said Jonathan Fraine of the University of Maryland, USA, lead author of the study. “In this case, we found clear skies on a distant planet. That’s lucky for us because it means clouds didn’t block our view of water molecules.”

    HAT-P-11b is a so-called exo-Neptune — a Neptune-sized planet that orbits another star. It is located 120 light-years away in the constellation of Cygnus (The Swan). Unlike Neptune, this planet orbits closer to its star, making one lap roughly every five days. It is a warm world thought to have a rocky core, a mantle of fluid and ice, and a thick gaseous atmosphere. Not much else was known about the composition of the planet, or other exo-Neptunes like it, until now.

    Part of the challenge in analysing the atmospheres of planets like this is their size. Larger Jupiter-like planets are easier to observe and researchers have already been able to detect water vapour in the atmospheres of some of these giant planets. Smaller planets are more difficult to probe — and all the smaller ones observed to date have appeared to be cloudy.

    The team used Hubble’s Wide Field Camera 3 and a technique called transmission spectroscopy, in which a planet is observed as it crosses in front of its parent star. Starlight filters through the rim of the planet’s atmosphere and into the telescope. If molecules like water vapour are present, they absorb some of the starlight, leaving distinct signatures in the light that reaches our telescopes.

    NASA Hubble WFC3
    WFC3 on Hubble

    “We set out to look at the atmosphere of HAT-P-11b without knowing if its weather would be cloudy or not,” said Nikku Madhusudhan, from the University of Cambridge, UK, part of the study team. “By using transmission spectroscopy, we could use Hubble to detect water vapour in the planet. This told us that the planet didn’t have thick clouds blocking the view and is a very hopeful sign that we can find and analyse more cloudless, smaller, planets in the future. It is groundbreaking!”

    Before the team could celebrate they had to be sure that the water vapour was from the planet and not from cool starspots — “freckles” on the face of stars — on the parent star. Luckily, Kepler had been observing the patch of sky in which HAT-P-11b happens to lie for years. Those visible-light data were combined with targeted infrared Spitzer observations. By comparing the datasets the astronomers could confirm that the starspots were too hot to contain any water vapour, and so the vapour detected must belong to the planet.

    The results from all three telescopes demonstrate that HAT-P-11b is blanketed in water vapour, hydrogen gas, and other yet-to-be-identified molecules. So in fact it is not only the smallest planet to have water vapour found in its atmosphere but is also the smallest planet for which molecules of any kind have been directly detected using spectroscopy. Theorists will be drawing up new models to explain the planet’s makeup and origins.

    Although HAT-P-11b is dubbed as an exo-Neptune it is actually quite unlike any planet in our Solar System. It is thought that exo-Neptunes may have diverse compositions that reflect their formation histories. New findings such as this can help astronomers to piece together a theory for the origin of these distant worlds.

    “We are working our way down the line, from hot Jupiters to exo-Neptunes,” said Drake Deming, a co-author of the study also from University of Maryland, USA. “We want to expand our knowledge to a diverse range of exoplanets.”

    The astronomers plan to examine more exo-Neptunes in the future, and hope to apply the same method to smaller super-Earths — massive, rocky cousins to our home world with up to ten times the mass of Earth. Our Solar System does not contain a super-Earth, but other telescopes are finding them around other stars in droves and the NASA/ESA James Webb Space Telescope, scheduled to launch in 2018, will search super-Earths for signs of water vapour and other molecules. However, finding signs of oceans and potentially habitable worlds is likely a way off.

    This work is important for future studies of super-Earths and even smaller planets. It could allow astronomers to pick out in advance the planets with atmospheres clear enough for molecules to be detected. Once again, astronomers will be crossing their fingers for clear skies.

    The international team of astronomers in this study consists of J. Fraine (University of Maryland, USA; Pontificia Universidad Católica de Chile, Chile; California Institute of Technology, USA); D. Deming (University of Maryland, USA; NASA Astrobiology Institute, USA); B. Benneke (California Institute of Technology, USA); H. Knutson (California Institute of Technology, USA); A. Jordán (Pontificia Universidad Católica de Chile, Chile); N. Espinoza (Pontificia Universidad Católica de Chile, Chile); N. Madhusudhan (University of Cambridge, UK); A. Wilkins (University of Maryland, USA); K. Todorov (ETH Zürich, Switzerland)

    See the full article, with notes, here.

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 11:55 am on September 22, 2014 Permalink | Reply
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    From Hubble: “Jets and explosions in NGC 7793″ 

    NASA Hubble Telescope

    Hubble

    22 September 2014
    No Writer Credit

    This new image from the NASA/ESA Hubble Space Telescope shows NGC 7793, a spiral galaxy in the constellation of Sculptor some 13 million light-years away from Earth. NGC 7793 is one of the brightest galaxies in the Sculptor Group, and one of the closest groups of galaxies to the Local Group — the group of galaxies containing our galaxy, the Milky Way and the Magellanic Clouds.

    lg
    Local Group

    ngc7793
    NGC7793
    Credit: NASA/ESA Hubble Acknowledgement: D. Calzetti (University of Massachusetts) and the LEGUS Team
    Hubble WFC3
    NASA Hubble WFC3

    mc
    Seen from the southern skies, the Large and Small Magellanic Clouds (the LMC and SMC, respectively) are bright patches in the sky. These two irregular dwarf galaxies, together with our Milky Way Galaxy, belong to the so-called Local Group of galaxies. Astronomers once thought that the two Magellanic Clouds orbited the Milky Way, but recent research suggests this is not the case, and that they are in fact on their first pass by the Milky Way. The LMC, lying at a distance of 160 000 light-years, and its neighbour the SMC, some 200 000 light-years away, are among the largest distant objects we can observe with the unaided eye. Both galaxies have notable bar features across their central discs, although the very strong tidal forces exerted by the Milky Way have distorted the galaxies considerably. The mutual gravitational pull of the three interacting galaxies has drawn out long streams of neutral hydrogen that interlink the three galaxies.
    Source ESO

    The image shows NGC 7793’s spiral arms and small central bulge. Unlike some other spirals, NGC 7793 doesn’t have a very pronounced spiral structure, and its shape is further muddled by the mottled pattern of dark dust that stretches across the frame. The occasional burst of bright pink can be seen in the galaxy, highlighting stellar nurseries containing newly-forming baby stars.

    Although it may look serene and beautiful from our perspective, this galaxy is actually a very dramatic and violent place. Astronomers have discovered a powerful microquasar within NGC 7793 — a system containing a black hole actively feeding on material from a companion star. While many full-sized quasars are known at the cores of other galaxies, it is unusual to find a quasar in a galaxy’s disc rather than at its centre.

    Micro-quasars are almost like scale models — they allow astronomers to study quasars in detail. As material falls inwards towards this black hole, it creates a swirling disc around it. Some of the infalling gas is propelled violently outwards at extremely high speeds, creating jets streaking out into space in opposite directions. In the case of NGC 7793, these jets are incredibly powerful, and are in the process of creating an expanding bubble of hot gas some 1000 light-years across.

    See the full article here.

    Another view:

    ngc7793S
    NGC 7793 as observed with the Spitzer Space Telescope as part of the Spitzer Infrared Nearby Galaxy Survey. The blue colors represent the 3.6 micrometre emission from stars. The green and red colors represent the 5.8 and 8.0 micrometre emission from polycyclic aromatic hydrocarbons and possibly dust.

    NASA Spitzer Telescope
    NASA/Spitzer

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 4:59 pm on September 18, 2014 Permalink | Reply
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    From Hubble- Hubblecast 77: Hubble and the Bermuda Triangle of space 

    NASA Hubble Telescope

    Hubble

    Hubblecast 77: Hubble and the Bermuda Triangle of space

    This Hubblecast tells the story of what happens to Hubble in the mysterious region known as the South Atlantic Anomaly. When satellites pass through this area they are bombarded with swarms of intensely high energy particles. This can produce “glitches” in astronomical data, malfunctioning of on-board electronics, and has even shut down unprepared spacecraft for weeks!

    van
    A cross-sectional view of the Van Allen radiation belts, noting the point where the South Atlantic Anomaly occurs.

    rosat
    Image of the South Atlantic Anomaly (SAA) taken by the ROSAT satellite. Image reflects the SAA at approximately 560Km.

    NASA ROSAT staellite
    NASA/ROSAT

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 12:59 pm on September 17, 2014 Permalink | Reply
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    From Hubble: “Big surprises can come in small packages” 

    NASA Hubble Telescope

    Hubble

    17 September 2014
    Contacts

    Anil Seth
    University of Utah
    Salt Lake City, Utah, USA
    Tel: +1-801-585-7793
    Cell: +1-206-724-3820
    Email: aseth@astro.utah.edu

    Remco van den Bosch
    Max Planck Institute for Astronomy
    Heidelberg, Germany
    Tel: +1-702-337-9424 (currently travelling in USA)
    Email: bosch@mpia.de

    Georgia Bladon
    ESA/Hubble, Public Information Officer
    Garching bei München, Germany
    Tel: +44 7816291261
    Email: gbladon@partner.eso.org

    Hubble helps astronomers find smallest known galaxy with supermassive black hole

    Astronomers using the NASA/ESA Hubble Space Telescope have found a monster lurking in a very unlikely place. New observations of the ultracompact dwarf galaxy M60-UCD1 have revealed a supermassive black hole at its heart, making this tiny galaxy the smallest ever found to host a supermassive black hole. This suggests that there may be many more supermassive black holes that we have missed, and tells us more about the formation of these incredibly dense galaxies. The results will be published in the journal Nature on 18 September 2014.

    bh

    Lying about 50 million light-years away, M60-UCD1 is a tiny galaxy with a diameter of 300 light-years — just 1/500th of the diameter of the Milky Way. Despite its size it is pretty crowded, containing some 140 million stars. While this is characteristic of an ultracompact dwarf galaxy (UCD) like M60-UCD1, this particular UCD happens to be the densest ever seen.

    Despite their huge numbers of stars, UCDs always seem to be heavier than they should be. Now, an international team of astronomers has made a new discovery that may explain why — at the heart of M60-UCD1 lurks a supermassive black hole with the mass of 20 million Suns.

    “We’ve known for some time that many UCDs are a bit overweight. They just appear to be too heavy for the luminosity of their stars,” says co-author Steffen Mieske of the European Southern Observatory in Chile. “We had already published a study that suggested this additional weight could come from the presence of supermassive black holes, but it was only a theory. Now, by studying the movement of the stars within M60-UCD1, we have detected the effects of such a black hole at its centre. This is a very exciting result and we want to know how many more UCDs may harbour such extremely massive objects.”

    The supermassive black hole at the centre of M60-UCD1 makes up a huge 15 percent of the galaxy’s total mass, and weighs five times that of the black hole at the centre of the Milky Way. “That is pretty amazing, given that the Milky Way is 500 times larger and more than 1000 times heavier than M60-UCD1,” explains Anil Seth of the University of Utah, USA, lead author of the international study. “In fact, even though the black hole at the centre of our Milky Way galaxy has the mass of 4 million Suns it is still less than 0.01 percent of the Milky Way’s total mass, which makes you realise how significant M60-UCD1’s black hole really is.”

    The team discovered the supermassive black hole by observing M60-UCD1 with both the NASA/ESA Hubble Space Telescope and the Gemini North 8-metre optical and infrared telescope on Hawaii’s Mauna Kea, USA. The sharp Hubble images provided information about the galaxy’s diameter and stellar density, whilst Gemini was used to measure the movement of stars in the galaxy as they were affected by the black hole’s gravitational pull. These data were then used to calculate the mass of the unseen black hole.

    Gemini North telescope
    Gemini North Interior
    Gemini Noth

    The finding implies that there may be a substantial population of previously unnoticed black holes. In fact, the astronomers predict there may be as many as double the known number of black holes in the local Universe.

    Additionally, the results could affect theories of how such UCDs form. “This finding suggests that dwarf galaxies may actually be the stripped remnants of larger galaxies that were torn apart during collisions with other galaxies, rather than small islands of stars born in isolation,” explains Seth. “We don’t know of any other way you could make a black hole so big in an object this small.”

    One explanation is that M60-UCD1 was once a large galaxy containing 10 billion stars, and a supermassive black hole to match. “This galaxy may have passed too close to the centre of its much larger neighbouring galaxy, Messier 60,” explains co author Remco van den Bosch of the Max Planck Institute for Astronomy in Heidelberg, Germany. “In that process the outer part of the galaxy would have been torn away to become part of Messier 60, leaving behind only the small and compact galaxy we see today.”

    The team believes that M60-UDC1 may one day merge with Messier 60 to form a single galaxy. Messier 60 also has its own monster black hole an amazing 4.5 billion times the size of our Sun and more than 1000 times bigger than the black hole in our Milky Way. A merger between the two galaxies would also cause the black holes to merge, creating an even more monstrous black hole.

    The international team of astronomers in this study consists of A.C. Seth (University of Utah, USA); R. van den Bosch (Max Planck Institute for Astronomy, Heidelberg, Germany); S. Mieske (European Southern Observatory, Chile); H. Baumgardt (University of Queensland, Australia); M. den Brok (University of Utah, USA); J. Strader (Michigan State University, USA); N. Neumayer (European Southern Observatory, Germany); I. Chilingarian (Smithsonian Astrophysical Observatory, USA; Moscow State University, Russia); M. Hilker (European Southern Observatory, Germany); R. McDermid (Australian Astronomical Observatory, Australia; Macquarie University, Australia); L. Spitler (Australian Astronomical Observatory, Australia; Macquarie University, Australia); J. Brodie (University of California, USA); M. J. Frank (Heidelberg University, Germany); J. L. Walsh (The University of Texas at Austin, USA).

    See the full article, with notes, here.

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 9:11 am on September 15, 2014 Permalink | Reply
    Tags: , , , , NASA/ESA Hubble   

    From Hubble: “An interacting colossus” 

    NASA Hubble Telescope

    Hubble

    This picture, taken by the NASA/ESA Hubble Space Telescope’s Wide Field Planetary Camera 2 (WFPC2), shows a galaxy known as NGC 6872 in the constellation of Pavo (The Peacock). Its unusual shape is caused by its interactions with the smaller galaxy that can be seen just above NGC 6872, called IC 4970. They both lie roughly 300 million light-years away from Earth.

    NASA Hubble WFPC2
    WFPC2 since retired

    ngc6872
    NGC6872 and IC4970
    Image credit: ESA/Hubble & NASA Acknowledgement: Judy Schmidt (geckzilla.com)

    From tip to tip, NGC 6872 measures over 500 000 light-years across, making it the second largest spiral galaxy discovered to date. In terms of size it is beaten only by NGC 262, a galaxy that measures a mind-boggling 1.3 million light-years in diameter! To put that into perspective, our own galaxy, the Milky Way, measures between 100 000 and 120 000 light-years across, making NGC 6872 about five times its size.

    The upper left spiral arm of NGC 6872 is visibly distorted and is populated by star-forming regions, which appear blue on this image. This may have been be caused by IC 4970 recently passing through this arm — although here, recent means 130 million years ago! Astronomers have noted that NGC 6872 seems to be relatively sparse in terms of free hydrogen, which is the basis material for new stars, meaning that if it weren’t for its interactions with IC 4970, NGC 6872 might not have been able to produce new bursts of star formation.

    A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Judy Schmidt.

    See the full article here.

    Another view

    ngc6872
    Source http://www.eso.org/gallery/v/ESOPIA/Galaxies/phot-20b-99-hires.jpg.html
    This image is a three-colour composite, this time reproduced from one blue (B), one green-yellow (V) and one red (R) exposure, obtained [by ESO/VLT] with FORS1 at ANTU in the morning of March 29, 1999.
    ESO FORS1
    ESO/FORS

    The field size is again 6.8×6.8 arcmin 2. It shows the spectacular barred spiral galaxy NGC 6872 that is shaped like an “integral sign”. It is of type SBb and is accompanied by a smaller, interacting galaxy, IC 4970 of type S0 (just above the centre). The bright object to the lower right of the galaxies is a star in the Milky Way whose image has been strongly overexposed and exhibits multiple optical reflections in the telescope and instrument. There are also many other, fainter and more distant galaxies of many different forms in the field. They are particularly well visible on the “Normal” and “Full Resolution” versions of the photo. The upper left spiral arm of NGC 6872 is significantly disturbed and is populated by a plethora of blueish objects, many of which are star-forming regions. This may have been be caused by a recent passage of IC 4970 through it. This interesting system is located in the southern constellation Pavo (The Peacock). It is comparatively distant, almost 300 million light-years away. It extends over more than 7 arcmin in the sky and its real size from tip to tip is thus nearly 750,000 light-years. It is in fact one of the largest known, barred spiral galaxies. In order to image all of this extraordinary object within the available field of the FORS1 camera, the instrument was rotated so that the galaxy extends along the diagonal. For this reason, the orientation is such that North is to the upper right and East is to the upper left.

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 1:56 pm on September 9, 2014 Permalink | Reply
    Tags: , , , , NASA/ESA Hubble   

    From Hubble: “Hubble Finds Companion Star Hidden for 21 Years in a Supernova’s Glare” 

    NASA Hubble Telescope

    Hubble

    Astronomers using NASA’s Hubble Space Telescope have discovered a companion star to a rare type of supernova. This observation confirms the theory that the explosion originated in a double-star system where one star fueled the mass-loss from the aging primary star.

    blow
    SN 1993J

    This detection is the first time astronomers have been able to put constraints on the properties of the companion star in an unusual class of supernova called Type IIb. They were able to estimate the surviving star’s luminosity and mass, which provide insight into the conditions that preceded the explosion.

    “A binary system is likely required to lose the majority of the primary star’s hydrogen envelope prior to the explosion. The problem is that, to date, direct observations of the predicted binary companion star have been difficult to obtain since it is so faint relative to the supernova itself,” said lead researcher Ori Fox of the University of California (UC) at Berkeley.

    Astronomers estimate that a supernova goes off once every second somewhere in the universe. Yet they don’t fully understand how stars explode. Finding a “smoking gun” companion star provides important new clues to the variety of supernovae in the universe. “This is like a crime scene, and we finally identified the robber,” quipped team member Alex Filippenko, professor of astronomy at UC Berkeley. “The companion star stole a bunch of hydrogen before the primary star exploded.”

    af
    Alex Filippenko

    The explosion happened in the galaxy M81, which is about 11 million light-years away from Earth in the direction of the constellation Ursa Major (the Great Bear). Light from the supernova was first detected in 1993, and the object was designated SN 1993J. It was the nearest known example of this type of supernova, called a Type IIb, due to the specific characteristics of the explosion. For the past two decades astronomers have been searching for the suspected companion, thought to be lost in the glare of the residual glow from the explosion.

    m81
    Messier 81
    The spiral galaxy Messier 81 is tilted at an oblique angle on to our line of sight, giving a “birds-eye view” of the spiral structure. The galaxy is similar to our Milky Way, but our favorable view provides a better picture of the typical architecture of spiral galaxies. Though the galaxy is 11.6 million light-years away, NASA Hubble Space Telescope’s view is so sharp that it can resolve individual stars, along with open star clusters, globular star clusters, and even glowing regions of fluorescent gas.

    Observations made in 2004 at the W.M. Keck Observatory on Mauna Kea, Hawaii, showed circumstantial evidence for spectral absorption features that would come from a suspected companion. But the field of view is so crowded that astronomers could not be certain if the spectral absorption lines were from a companion object or from other stars along the line of sight to SN 1993J. “Until now, nobody was ever able to directly detect the glow of the star, called continuum emission,” Fox said.

    Keck Observatory
    Keck Observatory Interior
    W. M. Keck Observatory

    The companion star is so hot that the so-called continuum glow is largely in ultraviolet (UV) light, which can only be detected above Earth’s absorbing atmosphere. “We were able to get that UV spectrum with Hubble. This conclusively shows that we have an excess of continuum emission in the UV, even after the light from other stars has been subtracted,” said team member Azalee Bostroem of the Space Telescope Science Institute (STScI), in Baltimore, Maryland.

    When a massive star reaches the end of its lifetime, it burns though all of its material and its iron core collapses. The rebounding outer material is seen as a supernova. But there are many different types of supernovae in the universe. Some supernovae are thought to have exploded from a single-star system. Other supernovae are thought to arise in a binary system consisting of a normal star with a white dwarf companion, or even two white dwarfs. The peculiar class of supernova called Type IIb combines the features of a supernova explosion in a binary system with what is seen when single massive stars explode.

    SN 1993J, and all Type IIb supernovae, are unusual because they do not have a large amount of hydrogen present in the explosion. The key question has been: how did SN 1993J lose its hydrogen? In the model for a Type IIb supernova, the primary star loses most of its outer hydrogen envelope to the companion star prior to exploding, and the companion continues to burn as a super-hot helium star.

    “When I first identified SN 1993J as a Type IIb supernova, I hoped that we would someday be able to detect its suspected companion star,” said Filippenko. “The new Hubble data suggest that we have finally done so, confirming the leading model for Type IIb supernovae.”

    The team combined ground-based data for the optical light and images from two Hubble instruments to collect ultraviolet light. They then constructed a multi-wavelength spectrum that matched what was predicted for the glow of a companion star.

    Fox, Filippenko, and Bostroem say that further research will include refining the constraints on this star and definitively showing that the star is present.

    The results were published in the July 20 Astrophysical Journal.

    See the full article here.

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 12:40 pm on September 9, 2014 Permalink | Reply
    Tags: , , , , NASA/ESA Hubble   

    From Hubble: “A spattering of blue” 

    NASA Hubble Telescope

    Hubble

    Far beyond the stars in the constellation of Leo (The Lion) is irregular galaxy IC 559

    irr
    Example of an irregular galaxy. The irregular galaxy NGC 1427A will not survive long as an identifiable galaxya, passing through the Fornax cluster at nearly 600 kilometers per second (400 miles per second). Galaxy clusters, like the Fornax cluster, contain hundreds or even thousands of individual galaxies. Within the Fornax cluster, there is a considerable amount of gas lying between the galaxies. When the gas within NGC 1427A collides with the Fornax gas, it is compressed to the point that it starts to collapse under its own gravity. This leads to formation of the myriad of new stars seen across NGC 1427A, which give the galaxy an overall arrowhead shape that appears to point in the direction of the galaxy’s high-velocity motion. The tidal forces of nearby galaxies in the cluster may also play a role in triggering star formation on such a massive scale.

    ic559
    IC559
    Credit: ESA/Hubble, NASA, D. Calzetti (UMass) and the LEGUS Team

    IC 559 is not your everyday galaxy. With its irregular shape and bright blue spattering of stars, it is a fascinating galactic anomaly. It may look like sparse cloud, but it is in fact full of gas and dust which is spawning new stars.

    Discovered in 1893, IC 559 lacks the symmetrical spiral appearance of some of its galactic peers and not does not conform to a regular shape. It is actually classified as a “type Sm” galaxy — an irregular galaxy with some evidence for a spiral structure.

    Irregular galaxies make up about a quarter of all known galaxies and do not fall into any of the regular classes of the Hubble sequence. Most of these uniquely shaped galaxies were not always so — IC 559 may have once been a conventional spiral galaxy that was then distorted and twisted by the gravity of a nearby cosmic companion.

    This image, captured by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3, combines a wide range of wavelengths spanning the ultraviolet, optical, and infrared parts of the spectrum.

    NASA Hubble WFC3

    See the full article here.

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 9:42 am on September 8, 2014 Permalink | Reply
    Tags: , , , , NASA/ESA Hubble   

    From SPACE.com: “How Many Galaxies Are There?” 

    space-dot-com logo

    SPACE.com

    April 01, 2014
    Elizabeth Howell
    Galaxies — those vast collections of stars that populate our universe — are all over the place. Perhaps the most resonant example of this fact is the Hubble eXtreme Deep Field, a collection of photographs from the Hubble Space Telescope revealing thousands of galaxies in a single composite picture.

    x
    Credit: NASA/ESA Hubble; G. Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R. Bouwens, Leiden University; and the HUDF09 Team)

    NASA Hubble Telescope
    NASA/ESA HUbble

    Estimating how many galaxies are throughout the universe is a tougher job, however. Sheer numbers is one problem — once the count gets into the billions, it takes a while to do the addition. Another problem is the limitation of our instruments. To get the best view, a telescope needs to have a large aperture (the diameter of the main mirror or lens) and be located above the atmosphere to avoid distortion from Earth’s air.

    While estimates among different experts vary, an acceptable range is between 100 billion and 200 billion galaxies, Mario Livio, an astrophysicist at the Space Telescope Science Institute in Baltimore, told Space.com.

    Going deep

    To the best of Livio’s knowledge, Hubble is the best instrument available for galaxy counting and estimation. The telescope, launched in 1990, initially had a distortion on its main mirror that was corrected during a shuttle visit in 1993. Hubble also went underwent several upgrades and service visits until the final shuttle mission there in May 2009.

    In 1995, astronomers pointed the telescope at what appeared to be an empty region of Ursa Major, and collected 10 days’ worth of observations. The result was an estimated 3,000 faint galaxies in a single frame, going as dim as 30th magnitude. (For comparison, the North Star or Polaris is at about 2nd magnitude.) This image composite was called the Hubble Deep Field and was the furthest anyone had seen into the universe at the time.

    hdf
    Hubble CDeep Field

    As the Hubble telescope received upgrades to its instruments, astronomers repeated the experiment twice. In 2003 and 2004, scientists created the Hubble Ultra Deep Field, which in a million-second exposure revealed about 10,000 galaxies in a small spot in the constellation Fornax.

    hudf
    Hubble Ultra Deep Field

    In 2012, again using upgraded instruments, scientists used the telescope to look at a portion of the Ultra Deep Field. Even in this narrower field of view, astronomers were able to detect about 5,500 galaxies. Researchers dubbed this the eXtreme Deep Field.

    edf
    Hubble eXtreme Deep Field

    All in all, Hubble reveals an estimated 100 billion galaxies in the universe or so, but this number is likely to increase to about 200 billion as telescope technology in space improves, Livio said.

    Counting stars

    Whatever instrument is used, the method of estimating the number of galaxies is the same. You take the portion of sky imaged by the telescope (in this case, Hubble). Then — using the ratio of the sliver of sky to the entire universe — you can determine the number of galaxies in the universe.

    “This is assuming that there is no large cosmic variance, that the universe is homogenous,” Livio said. “We have good reasons to suspect that is the case. That is the cosmological principle.”

    The principle dates back to Albert Einstein’s theory of general relativity at the turn of the last century. One of general relativity’s findings is that gravity is a distortion of space and time. With that understanding in hand, several scientists (including Einstein) tried to understand how gravity affected the entire universe.

    “The simplest assumption to make is that if you viewed the contents of the universe with sufficiently poor vision, it would appear roughly the same everywhere and in every direction,” NASA stated. “That is, the matter in the universe is homogeneous and isotropic when averaged over very large scales. This is called the cosmological principle.”

    One example of the cosmological principle at work is the cosmic microwave background, radiation that is a remnant of the early stages of the universe after the Big Bang. Using instruments such as NASA’s Wilkinson Microwave Anisotropy Probe, astronomers have found the CMB is virtually identical wherever one looks.

    Cosmic Background Radiation Planck
    CMB from ESA/Planck

    Would the number of galaxies change with time?

    Measurements of the universe’s expansion — through watching galaxies race away from us — show that it is about 13.82 billion years old. As the universe gets older and bigger, however, galaxies will recede farther and farther from Earth. This will make them more difficult to see in telescopes.

    The universe is expanding faster than the speed of light (which does not violate Einstein’s speed limit because the expansion is of the universe itself, rather than of objects traveling through the universe). Also, the universe is accelerating in its expansion.

    This is where the concept of the “observable universe” — the universe that we can see — comes into play. In 1 trillion to 2 trillion years, Livio said, this means that there will be galaxies that are beyond what we can see from Earth.

    “We can only see light from galaxies whose light had enough time to reach us,” Livio said. “It doesn’t mean that that’s all there is in the universe. Hence, the definition of the observable universe.”

    Galaxies also change over time. The Milky Way is on a collision course with the nearby Andromeda Galaxy, and both will merge in about 4 billion years. Later on, other galaxies in our Local Group — the galaxies closest to us — will eventually combine. Residents of that future galaxy would have a much darker universe to observe, Livio said.

    Local Group
    Local Group

    “Civilizations started then, they would have no evidence that there was a universe with 100 billion galaxies,” he said. “They would not see the expansion. They would probably not be able to tell there was a Big Bang.”

    What about other universes?

    As the early universe inflated, there are some theories that say that different “pockets” broke away and formed different universes. These different places could be expanding at different rates, include other types of matter, and have different physical laws than our own universe.

    Livio pointed out there could be galaxies in these other universes — if they exist — but we have no way right now of knowing for sure. So the number of galaxies could even be greater than 200 billion, when considering other universes.

    In our own cosmos, Livio said, astronomers will be better able to refine the number upon the launch of the James Webb Space Telescope (for which his institute will manage the mission operations and science). Hubble is able to peer back at galaxies that formed about 450 million years after the Big Bang. After James Webb launches in 2018, astronomers anticipate they can look as far back as 200 million years after the Big Bang.

    NASA Webb Telescope
    NASA/Webb

    “The numbers are not going to change much,” Livio added, pointing out the first galaxies probably formed not too long before that. “So a number like 200 billion [galaxies] is probably it for our observable universe.”

    See the full article here.

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  • richardmitnick 8:29 am on September 1, 2014 Permalink | Reply
    Tags: , , , , NASA/ESA Hubble   

    From Hubble: “Spiral in Serpens” 

    NASA Hubble Telescope

    Hubble

    September 1, 2014

    This new NASA/ESA Hubble Space Telescope image shows a beautiful spiral galaxy known as PGC 54493, located in the constellation of Serpens (The Serpent). This galaxy is part of a galaxy cluster that has been studied by astronomers exploring an intriguing phenomenon known as weak gravitational lensing.

    pbc
    Credit: NASA/ESA Hubble Judy Schmidt
    Hubble Space Telescope ACS

    NASA Hubble ACS
    ACS

    This effect, caused by the uneven distribution of matter (including dark matter) throughout the Universe, has been explored via surveys such as the Hubble Medium Deep Survey. Dark matter is one of the great mysteries in cosmology. It behaves very differently from ordinary matter as it does not emit or absorb light or other forms of electromagnetic energy — hence the term “dark”.

    Even though we cannot observe dark matter directly, we know it exists. One prominent piece of evidence for the existence of this mysterious matter is known as the “galaxy rotation problem“. Galaxies rotate at such speeds and in such a way that ordinary matter alone — the stuff we see — would not be able to hold them together. The amount of mass that is “missing” visibly is dark matter, which is thought to make up some 27% of the total contents of the Universe, with dark energy and normal matter making up the rest. PGC 55493 has been studied in connection with an effect known as cosmic shearing. This is a weak gravitational lensing effect that creates tiny distortions in images of distant galaxies.

    A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Judy Schmidt.

    See the full article here.

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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